1. Field of the Invention
The present invention relates to the preparation of an artificial sweetener, and more particularly to the preparation of APM in an encapsulated form suitable for incorporation in food products, such as chewing gums and candies which exhibits improved shelf stability in such food products.
2. Description of the Prior Art
The sweetening agent known as APM comprises a dipeptide that is chemically identified as L-aspartyl-L-phenylalanine methyl ester, and is described in U.S. Pat. No. 3,492,131, the disclosure of which is incorporated herein by reference. Since its development, APM has been widely recognized as a desirable artificial sweetener having particular utility for incorporation in chewing gum as disclosed by U.S. Pat. No. 3,943,258, to Bahoshy et al.
Several problems have been observed with APM, among them that it breaks down in contact with water, and in contact with certain flavors such as cinnamon. Also, APM tends to break down from exposure to elevated temperatures. In the instance where APM is incorporated in chewing gums, the relatively high temperatures of storage and shipment of the product and contact of the gum with water, tend to cause the APM to break down, and lessens sweetness. In particular, high temperatures have been found to induce the ester linkage to hydrolyze to the dipeptide aspartylphenylalanine which in turn cyclizes to the corresponding diketopiperazine, in which last form sweetness is substantially lessened. Several methods of preparing the APM for incorporation into chewing gums have been proposed that attempt to alleviate this problem by rendering the APM more stable. For example, U.S. Pat. Nos. 4,122,195 and 4,139,639, both to Bahoshy et al., propose to fix APM by preparing it with a material such as gum arabic or the reaction product of a compound containing a polyvalent metallic ion, with an ungelatinized starch acid-ester of a substituted dicarboxylic acid, by a spray drying technique, where the APM and the film former are prepared in an emulsion.
While the foregoing technique is reported to show some improvement in shelf stability, relatively rapid breakdown of APM still occurs. Also, the relatively large amount of APM being stabilized, results in reduced intensity of sweetness release, which is a particularly important attribute of a commercially successful chewing gum.
It is therefore desirable to develop a method for preparing APM in a manner which increases the shelf stability of APM in products to which APM is added.